1. Field of the Invention
This invention relates to photo-optical scanning apparatus utilizing a laser diode light generating device and a polygonal mirror assembly in conjunction with suitable light beam collimating and focussing apparatus. More specifically, the invention relates to a system for precisely shaping the laser generating light beam into an efficient spot scanning size for electrophotographic printing and/or copying.
2. Description of the Prior Art
Many problems are associated with scanning systems wherein a modulated/or unmodulated light beam is caused to scan by means of a rotatable polygonal mirror. For example the position of each scanning line becomes difficult to control. This problem is a result of the angular relationship between adjacent facets of the polygon as well as between the facet planes and the rotational axis of the polygon.
Another problem is associated with the location of the laser light generating apparatus and its angular relationship to the operably associated hardware. A further problem is that as the polygon mirror assembly is rotated at a constant rotational rate the speed of the generated spot will be constant along an arc but will not be constant with respect to a straight line scan. In fact, the laser beam or spot speeds up at the periphery of the scan line which in turn has the effect of changing the dimension of the output data being developed. These and other similarly associated problems have caused many of the prior art devices to be less than commercially satisfactory.